A few winters ago I noticed some water damage on an interior wall of our building. I traced it back to what I think is the source: a leaking interior roof drain. It seems that ice formed inside the drain and the expansion caused a sizable crack.

Can anyone offer advice on how to repair this problem? I don't have much experience with roof repair so any help would be much appreciated. I have tried using a sealer designed for gutters but it lasted only a short while before it started leaking again. I have attached a few pictures of the problem for reference.